ASTR-101 Section 004 Lecture 9 Rare Earth? John T. McGraw, Professor

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1 ASTR-101 Section 004 Lecture 9 Rare Earth? John T. McGraw, Professor

2 Rare Earth Long-lived sun Rocky world C, O, Si, materials for soil, tools and subsistence Near circular orbit Not too warm not too cold just right! Not too massive not too light just right! Radioactive core constituents are important see plate tectonics! An atmosphere not too thick (Venus) - not too thin (Mars) just right! Magnetic shield from energetic particles Liquid water the universal solvent, water exists as solid liquid and gas Plate tectonics! Diversity! Evolution! Longevity! (You know that Venus and Mars don t have tectonics.) A moon to stir the brew (including molten rock!) only one moon! Not too close to other stars Not too much killer material left in the solar nebula But we don t know our own place and our effect on the world!

3 The Earth s atmosphere, oceans, and surface are extraordinarily active All activity in the Earth s atmosphere, oceans, and surface is powered by three sources of energy

4 The Earth s Dynamic Atmosphere and Surface

5 Tidal forces from the Moon and Sun help to power the motion of the oceans

6 The Greenhouse Effect Solar energy is the energy source for the atmosphere In the greenhouse effect, some of this energy is trapped by infrared absorbing gases in the atmosphere, raising the Earth s surface temperature

7 The internal heat of the Earth is the energy source for geologic activity

8 Studies of earthquakes reveal the Earth s layered interior structure

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10 Seismologists deduce the Earth s interior structure by studying how longitudinal P waves and transverse S waves travel through the Earth s interior

11 Plate movement produces earthquakes, mountain ranges, and volcanoes that shape the Earth s surface The Earth s crust and a small part of its upper mantle form a rigid layer called the lithosphere. The lithosphere is divided into huge plates that move about over the plastic layer called the asthenosphere in the upper mantle

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15 Plate tectonics, or movement of the plates, is driven by convection within the asthenosphere Molten material wells up at oceanic rifts, producing seafloor spreading, and is returned to the asthenosphere in subduction zones As one end of a plate is subducted back into the asthenosphere, it helps to pull the rest of the plate along

16 Plate tectonics is responsible for most of the major features of the Earth s surface, including mountain ranges, volcanoes, and the shapes of the continents and oceans

17 Plate tectonics is involved in the formation of the three major categories of rocks: igneous rocks cooled from molten material sedimentary rocks formed by the action of wind, water, and ice metamorphic rocks altered in the solid state by extreme heat and pressure

18 A bow-shaped shock wave, where the supersonic solar wind is abruptly slowed to subsonic speeds, marks the outer boundary of the magnetosphere

19 An increased flow of charged particles from the Sun can overload the Van Allen belts and cascade toward the Earth, producing aurorae Some charged particles from the solar wind are trapped in two huge, doughnut-shaped rings called the Van Allen belts

20 Evolution on Earth s Surface

21 The Earth s atmosphere has changed substantially over our planet s history The Earth s atmosphere differs from those of the other terrestrial planets in its chemical composition, circulation pattern, and temperature profile The Earth s atmosphere evolved from being mostly water vapor to being rich in carbon dioxide A strong greenhouse effect kept the Earth warm enough for water to remain liquid and to permit the evolution of life

22 The appearance of photosynthetic living organisms led to our present atmospheric composition, about four-fifths nitrogen and one-fifth oxygen

23 The Earth s atmosphere is divided into layers called the troposphere, stratosphere, mesosphere, and thermosphere Ozone molecules in the stratosphere absorb ultraviolet light

24 Circulation in our atmosphere results from convection and the Earth s rotation Because of the Earth s rapid rotation, the circulation in its atmosphere is complex, with three circulation cells in each hemisphere

25 A burgeoning human population is profoundly altering the Earth s biosphere

26 The Distribution of Plant Life Land colors designate vegetation: dark green for the rain forests, light green and gold for savannas and farmland, and yellow for the deserts Ocean colors show that phytoplankton are most abundant in the red and orange areas and least abundant in the dark blue areas

27 Deforestation and the burning of fossil fuels are increasing the greenhouse effect in our atmosphere and warming the planet

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29 The Earth is warming up. Is this a natural effect? Does it make any difference if it is natural or not?

30 Proxy measurements indicate that the Earth is warmer now than in the past 2000 years, and that carbon dioxide in the atmosphere is at an all-time high value.

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32 Industrial chemicals released into the atmosphere have damaged the ozone layer in the stratosphere The ozone hole has healed itself dramatically, presumably because of limiting industrial chemicals.